Galacto-oligosaccharide synthesis using immobilized β-galactosidase

Galacto-oligosaccharides (GOS) are carbohydrates generated from glucose and galactose, which exhibit prebiotic functionality. In the colon they selectively stimulate the growth of beneficial bacteria.
This thesis provides an overview of historical and current literature on the synthesis of (galacto-)oligosaccharides and describes the enzyme (beta-galactosidase) and the mechanism of synthesis.
The selection of a suitable carrier for the immobilization was carried out by application of the Analytical Hierarchy Process (AHP). Application of AHP methodology lead to the same outcome as when a model for the cost price calculation per cycle of GOS synthesis was applied.
The application of the immobilized enzyme in a batch- as well as a continuous system is described. In the batch process the synthesis of GOS starting from a lactose slurry instead of the more commonly described lactose solution was given attention. The enzymatic and the volumetric productivities of the systems were compared with those of a free enzyme system. Additionally, the compositions of the GOS mixture were compared.
The formation of allo-lactose during the GOS synthesis, catalyzed by B. circulans beta-galactosidase, is further discussed. The reaction is kinetically controlled reaction makes the rate of allo-lactose formation dependent of the enzyme dosage. The preferential substrate utilization of the enzyme lead to accumulation of allo-lactose.
This study shows that the use of an immobilized enzyme system can contribute to a more cost-efficient and more sustainable process for the synthesis of GOS.